The present invention relates to a disc apparatus which uses an exchangeable disc enclosed in a cartridge as a recording medium and, more particularly, to an optical disc apparatus for properly controlling a load motor to execute the loading operation and the unloading operation of an optical disc enclosed in a cartridge and for executing an initialization control during the acceleration of a spindle motor.
In an optical disc apparatus, memory capacity is very large and effective use as a memory device of a large capacity of a computer system is expected and miniaturization is also expected.
Among them, in the exchangeable optical disc apparatus, an optical disc enclosed in a cartridge is used as a recording medium. The loading operation when the cartridge is inserted into the optical disc apparatus and the unloading operation when the cartridge is taken out of the apparatus are automatically executed by a load motor. In order to certainly execute the loading and unloading operations without imposing a burden on the optical disc, it is demanded to properly control a driving torque of the load motor. In the exchangeable optical disc apparatus, further, it is demanded to limit a current consumption to thereby make it unnecessary to use a power source unit of a large current capacity and to reduce the size and costs.
Hitherto, the optical disc which is used in the optical disc apparatus in which a recording medium can be exchanged is ordinarily enclosed in a cartridge casing. When the cartridge casing is inserted into the optical disc apparatus, a shutter of the cartridge casing is opened by a shutter opening/closing mechanism in the apparatus, so that a hub for chucking of the optical disc and the disc surface that is accessed by an optical head are exposed. The chucking operation of the optical disc to a rotary shaft of a spindle motor is performed by driving a loading mechanism by the load motor. The optical disc is moved in the direction of the rotary shaft of the spindle motor by the loading operation. The optical disc is finally adsorbed and fixed by a magnet provided for a disc holding plate of the spindle rotary shaft. To reduce the costs of the apparatus, in the driving of the load motor, generally, a switching circuit which is known as a bridge driver is used. That is, by turning on or off a switching circuit which can switch the direction of a drive current by an instruction from an MPU, the load motor is rotated in the forward direction, thereby executing the loading operation. By rotating the load motor in the opposite direction, the unloading operation is executed.
In such a conventional control of the load motor to execute the loading operation and unloading operation of the optical disc enclosed in the cartridge casing, since the voltage which is applied to the load motor is fixed, the rotational speed of the motor depends on the torque of the motor. Therefore, when a motor of a large torque is used, speeds of the loading operation and unloading operation rise. However, since the burden which is imposed on the loading mechanism increases, the life of the load motor decreases. In the case where the optical disc apparatus is used as what is called a stand-alone apparatus in which the optical disc apparatus is enclosed as a deck in a jukebox or the like, the life of the loading mechanism is a very important performance. On the contrary, when the motor of a small torque is used, although the life of the loading mechanism is long, the times which are required for the loading operation and unloading operation increase.
Ordinarily, the chucking of the optical disc is performed by a magnet and, in the loading mode, the optical disc is attracted by the magnet. Therefore, it is sufficient to use a motor of a small torque. On the contrary, in the unloading mode to eject out the cartridge, the disc is removed from the magnet. Therefore, the operation can be quickly executed by using a motor of a large torque. Further, when the torque is small, the optical disc cannot be unloaded. Therefore, by constructing in a manner such that the voltage which is applied to the load motor can be changed from a firmware such as an MPU or the like and the torque is reduced in the loading mode and the torque is increased in the unloading mode, the operation can be promptly executed and the life of the loading mechanism can be also elongated. However, to enable the voltage that is applied to the motor to be changed from the firmware such as an MPU or the like, there is a problem such that a voltage controlled circuit must be added and the apparatus is complicated and the costs rise.
On the other hand, in the conventional optical disc apparatus in which the recording medium can be exchanged, when the medium such as optical disc, magnetooptic disc, or the like is exchanged by the loading mechanism in a motor stop state, the spindle motor is activated on the basis of a detection signal of the completion of the loading operation. The rotational speed of the spindle motor is raised to a predetermined speed of, for example, 3600 r.p.m. and when the speed reaches the predetermined rotational speed, a light emission adjustment to adjust a laser diode LD of the head, a focusing adjustment to execute a focusing servo by searching and moving an objective lens in a predetermined range, and the like are executed in order to obtain predetermined read power and write power. After completion of the above series of initialization adjusting processes, a ready state in which data can be written or read out is set. However, when the motor speed reaches the predetermined speed after the medium had been exchanged, so long as the series of initialization adjusting processes such as light emission adjustment of the laser diode, focus executing adjustment, and the like are executed and a ready state is subsequently set to thereby enable data to be written or read out, there is a problem such that a processing time in which the initialization processing time has been added to the leading time of the motor rotation is needed and the waiting time until the ready state is long. Therefore, in order to reduce the waiting time until the ready state in which data can be written or read out after the medium was exchanged as short as possible, the present inventors et al. have proposed an optical disc apparatus which executes the initialization control such as light emission adjustment of the laser diode, executing adjustment of the focusing servo, and the like during the raising operation of the motor rotational speed (JP-A-3-104020).
In the conventional disc apparatus, however, in the initialization adjusting processes which are executed during the raising operation of the motor rotational speed, there is a case where a voice coil motor is simultaneously driven to move the head. Therefore, in addition to a control current of the spindle motor, a control current of the voice coil motor flows. When the spindle motor and the voice coil motor are simultaneously driven, fairly large currents respectively flow when they are seen from the whole apparatus. For instance, in case of the optical disc of 5 inches, the peak current reaches up to about 5 A. Thus, there are problems such that the peak value of the current consumption of the whole optical disc apparatus increases and it is necessary to use a power source of a large current capacity and the use of such a large power source obstructs the realization of a small size and low costs.